Unit 4: Cell Communication

• Endocrine system: Secretes hormones into blood from ductless glands that coordinate slower but longer-acting responses
• Paracrine: Signals act on cells near the secreting cell
• Local regulators: Chemical signals that travel over short distances due to diffusion
• Signal Transduction: The linkage of mechanical, chemical, or electromagnetic stimulus to a specific cellular response
• Hormone: A regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.
• Neurohormones: A hormone produced by nerve cells and secreted into the circulation.
• Epinephrine: A hormone secreted by the adrenal glands, especially in conditions of stress.
• Negative Feedback: The diminution or counteraction of an effect by its own influence on the process giving rise to it, as when a high level of a particular hormone in the blood may inhibit further secretion of that hormone, or where the result of a certain action may inhibit further performance of that action.
• Growth Hormone: hormone secreted by anterior pituitary gland that usually stimulates growth of bones
• second messengers: Small, non-protein water soluble molecules or ions that send messages throughout the cells by diffusion.
• Plant growth regulator: Organic compounds other than nutrients (like hormones that affect plant growth.
• plant hormone: abscisic acid, auxin, cytokinins, ethylene, gibberellins act as chemical messengers
• phototropism: Growth of a plant shoot toward or away from light.
• circadian rhythms: The 24-hour biological cycles found in humans and many other species.
• biotic stresses: Stresses caused by living factors, such as bacteria, fungi, animals, other plants.
• heat-shock proteins: Proteins that help maintain integrity of other proteins that would normally be denatured in extreme heat.
• anaphase: fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell
• binary fission: the type of cell division by which prokaryotes reproduce; each dividing daughter cell receives a copy of the single parental chromosome
• cell cycle: an ordered sequence of events in the life of a eukaryotic cell, from its origin in the division of a parent cell until its own division into two; composed of M, G1, S, G2
• cell cycle control system: a cyclically operating set of molecules in the cell that triggers and coordinates key events in the cell cycle
• cell division: reproduction of a cell
• cell plate: a double membrane across the midline of a dividing plant cell, between which the new cell wall form during cytokinesis
• centromere: the centralized region joining two chromatids
• checkpoint: a critical control point in the cell cycle where stop and go-ahead signals regulate the cycle
• chromatin: complex of DNA and proteins that makes up a eukaryotic chromosome; when a cell is not diving it exists as a mass of very long, thin fibers that are not visible with a light microscope
• chromosome: a threadlike, gene-carrying structure found in the nucleus; each consists of one very long DNA molecule and associated proteins
• cleavage furrow: the first sign of cleavage in an animal cell; a shallow groove in the cell surface near the old metaphase plate
• cyclin: a regulatory protein whose concentration fluctuates cyclically
• cyclin-dependent kinase (Cdk): a protein kinase that is only active when attached to a particular cyclin
• cytokinesis: the division of the cytoplasm to form two separate daughter cells immediately following mitosis
• G0 phase: a nondividing state in which a cell has left the cell cycle
• G1 phase: The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.
• genome: the complete set of genes or genetic material present in a cell or organism.
• growth factor: a protein that must be present in the extracellular environment for growth and normal development of certain types of cells; a local regulator that acts on nearby cells to stimulate cell proliferation and differentiation
• interphase: the period in the cell cycle when the cell is not dividing; cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. 90% of the cell cycle
• M phase: mitotic phase; the phase of the cell cycle that includes mitosis and cytokinesis
• meiosis: a two-stage type of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell
• metaphase: the third stage of mitosis, in which the spindle is complete and the chromosomes, attached to the microtubules at their kinetochores, are all aligned at the plate
• mitosis: a process of nuclear division in eukaryotic cells conventionally divided into 5 stages; prophase, prometaphase, metaphase, anaphase, and telophase; conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei
• mitotic (M) phase: the phase of the cell cycle that includes mitosis and cytokinesis